The clutch release of gearboxes can be effected by virtue of clutch actuators arranged externally on the clutch bell housing or by means of clutch release mechanisms arranged centrally on the input shaft of the gearbox. In the latter variant there is no need to provide a transmission lever between the clutch and the clutch actuator. This lever amplifies the force produced by the clutch actuator to the force required at the clutch in order to disengage the clutch disc from the flywheel between the drive motor and the gearbox.
From European patent specification EP 0 371 975 a clutch release system is known, in which an actuation cylinder, magnetic valves and a path measurement device are provided in a clutch actuator not located centrally. The clutch release system comprises only one external connection for the actuation medium and one external connection for electrical leads. In this clutch release system it is necessary to provide both an additional lead to the clutch control device and an additional line for the supply of the actuation medium. There must also be a lever mechanism between the clutch actuator and the clutch.
German application DE 198 26 068.7 describes a central clutch release system in which an actuation cylinder for the actuation medium and a path measurement device are arranged centrally around the input shaft of the gearbox. The valves are arranged outside the gearbox and have to be connected with the actuation cylinder by means of a corresponding connection line. An electrical lead must also be provided for the connection between the path measurement device and a clutch control unit.
From European patent specification EP 0 824 644 a transmission control system for vehicle transmissions is known, which is arranged on or in the gearbox and co-operates with control elements of the gear-shift mechanisms. The transmission control system comprises both mechanical and electronic elements. The transmission control system does not co-operate with a clutch release or clutch control unit.
Beginning from the said state of the prior art, the purpose of the present invention is to propose a centrally operating clutch release system for a gearbox which eliminates the existing disadvantages.
The objective is achieved by a clutch release system having the characteristics of claim 1. Its design features are the object of the subordinate claims.